I'm knitting this right now as well. My pattern has a sticker on the back that says something to the effect of "if you have trouble picking up enough stitches, look at my website http://www.knittingpureandsimple.com
for helpful hints." If you go to her website, then go to the FAQ page, there is information to help you out. You'll do basically as Sue says, pick up 2 stitches in 1 every once in a while. You stitch the first one under both legs of the edge, then stitch the second by picking up only 1 leg. It's worth the trouble, mine is coming out so cute!